Automatically creating multiple replication sessions in response to a single replication command entered by a user

ABSTRACT

A technique performs replication. The technique involves receiving, by processing circuitry, a virtual storage processor (VSP) replication command from a user. The VSP replication command specifies a source VSP and a destination VSP (e.g., configuration data which defines an operating environment). The technique further involves identifying, by the processing circuitry and in response to the VSP replication command, multiple source data objects which are configured to store data from the context of the source VSP. The technique further involves automatically creating, after the multiple source data objects are identified, multiple replication sessions to replicate the multiple source data objects as multiple destination data objects which are configured to store data from the context of the destination VSP. Once created, the entire lifecycle of the replication session occurs at the VSP level and replication of the internals of the VSP are entirely hidden from the end user.

BACKGROUND

A typical data storage production site includes one or more physicaldata movers (e.g., storage processors or blades) and storage devices(e.g., flash memory units, magnetic disk drives, etc.). In someconventional file-based production sites, each physical data mover runsits own operating system and one or more instances of a Common InternetFile System (CIFS) server, i.e., a logical server that uses the CIFSprotocol to transfer files. During operation, the physical data moversretrieve data from the storage devices and make that data available toone or more network clients.

Some data storage systems are capable of performing file systemreplication to replicate source file systems from production sites toreplica sites. File system replication is a service that produces aread-only point-in-time copy of a source file system at a replica site,and periodically updates this copy to make it is consistent with thesource file system. In a CIFS environment, to make files fullyfunctional and accessible at a replica site, a virtual data mover (VDM)for the source file system is also replicated from the production siteto the replica site. The VDM defines the complete CIFS workingenvironment including local groups, user mapping information, Kerberosobjects, shares, event logs, and Registry information. Certain detailsof VDMs and replication for a data storage system similar to thatmentioned above are described in a document entitled “Using EMC®CelerraReplicator™ (V2),” dated February 2009, the contents and teachings ofwhich are hereby incorporated by reference in their entirety.

Suppose that several user file systems are supported by a VDM on aproduction site, and that a data storage system administrator now wishesto replicate these user file systems to a replica site. As part of thereplication process, the administrator first enters a set ofinstructions into a command line interface to start a VDM replicationsession which replicates the VDM from the production site to the replicasite. Then, the administrator individually enters additional sets ofinstructions to start separate user file system replication sessions toreplicate the user files systems from the production site to the replicasite.

SUMMARY

Unfortunately, there are deficiencies to the above-describedconventional replication approach in which an administrator manuallyenters sets of instructions to individually create replication sessionsto replicate user file systems to a replica site. In particular, theremay exist many user file systems requiring replication thus making thenumber of replication sessions required to meet the goals of theadministrator quite high. In this situation, the administrator mustidentify all of the user file systems and, manually create a replicationsession for each user file system one at a time. Otherwise, one or moreof the user file systems will not be replicated from the production siteto the replica site.

Additionally, the data storage system topology may be complex. Forexample, the goals of the administrator may include setting upone-to-many configurations (i.e., one source and multiple destinations)and/or cascade configurations (i.e., a destination in one replicationsession serving as a source in another replication session). For suchtopologies, the burden on the administrator and the associatedcomplexity can grow exponentially.

Furthermore, the task of correctly typing the instructions may beburdensome and prone to human error, particularly if the administratoris not well-trained or comfortable with the syntax. That is, theinstruction lines typically include a cryptic language formed bycombining specific instruction names, option names, and names of datastorage objects. Accordingly, the work of the administrator may beextremely tedious and time consuming.

In contrast to the above-described conventional replication approach inwhich an administrator must manually enter separate sets of instructionsto individually create replication sessions to replicate user filesystems to a replica site, improved techniques are directed toautomatically creating multiple replication sessions in response to asingle replication command from a user. Such a command directs creationof a virtual storage processor (VSP) replication session to reliably androbustly replicate a file system environment, and further directscreation of standalone file system replication sessions to replicateseparate user file systems. Along these lines, the necessary replicationinformation for creating the replication sessions can be derivedautomatically from records in a configuration database. Accordingly, theuser is required to simply enter one replication command regardless ofthe number of user file systems being replicated and irrespective of thedata storage system topology. As a result, there is little or noopportunity for error, and the work of the user is less tedious and timeconsuming.

One embodiment is directed to a method of performing replication. Themethod includes receiving, by processing circuitry, a VSP replicationcommand from a user. The VSP replication command specifies a source VSPand a destination VSP (e.g., configuration data which defines anoperating environment). The method further includes identifying, by theprocessing circuitry and in response to the VSP replication command,multiple source data objects which are configured to store data from thecontext of the source VSP. The method further includes automaticallycreating, after the multiple source data objects are identified,multiple replication sessions to replicate the multiple source dataobjects as multiple destination data objects which are configured tostore data from the context of the destination VSP.

In some arrangements, a configuration database holds multiple VSPrecords corresponding to multiple VSPs. In these arrangements,identifying the multiple source data objects includes (i) locating, fromthe configuration database, a set of VSP records corresponding to thesource VSP, and (ii) ascertaining, from the set of VSP records, themultiple source data objects which are configured to store data from thecontext of the source VSP.

In some arrangements, ascertaining the multiple source data objectsincludes constructing a list of lower-deck files from the set of VSPrecords. Each lower-deck file on the list is one of the multiple sourcedata objects.

In some arrangements, at least some lower-deck files contain upper-deckfile systems of upper-deck files. In these arrangements, the method mayfurther include mounting, prior to creating the multiple replicationsessions, the upper-deck file systems to a root file system of thesource VSP.

In some arrangements, a configuration file system is contained within aparticular lower-deck file. The VSP configuration file system has VSPconfiguration files which store VSP configuration data (i.e.,configuration data defining a specific operating environment for theupper-deck file systems). In these arrangements, creating the multiplereplication sessions includes establishing a VSP configuration filesystem replication session to replicate the VSP configuration filesystem from the source VSP to the destination VSP.

In some arrangements, a set of user file systems is contained within aset of lower-deck files. The set of user files systems have user fileswhich store host data. In these arrangements, creating the multiplereplication sessions further includes establishing a set of user filesystem replication sessions to replicate the set of user file systems tothe destination VSP. Each user file system replication session is astandalone session which is independent of the other user file systemreplication sessions.

In some arrangements, host applications provide host input/output (I/O)requests to load and store host data. In these arrangements, the methodfurther includes storing, in response to host I/O requests and duringthe multiple replication sessions, (i) host data in at least some of thesource data objects from the context of the source VSP and (ii) copiesof the host data in at least some of the destination data objects fromthe context of the destination VSP.

Such storing may involve identifying block changes to the source dataobjects and applying the block changes to the destination data objects.In some arrangements, the source VSP resides on a first physical storageprocessor, and the destination VSP resides on a second physical storageprocessor. In these arrangements, applying the block changes to thedestination data objects includes conveying the block changes from thefirst physical storage processor to the second physical storageprocessor through a wide area network (WAN).

In some arrangements, each source data object is initially in a hostread/write state, and each destination data object is initially in ahost read-only state. In these situations, the method further includestransitioning, in response to a failover event in which replication of afile system contained in a particular source data object to a particulardestination data object is stopped, the particular destination dataobject from the host read-only state to the host read/write state whileother replication sessions of the multiple replication sessions continueto operate.

It should be understood that, in the cloud context, electronic circuitryis formed by remote computer resources distributed over a network. Sucha computing environment is capable of providing certain advantages suchas enhanced fault tolerance, load balancing, processing flexibility,etc.

Other embodiments are directed to electronic systems and apparatus,processing circuits, computer program products, and so on. Someembodiments are directed to various methods, electronic components andcircuitry which are involved in performing replication.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages will be apparent fromthe following description of particular embodiments of the invention, asillustrated in the accompanying drawings, in which like referencecharacters refer to the same parts throughout the different views. Inthe accompanying drawings,

FIG. 1 is a block diagram showing an example data storage apparatus inan environment wherein improved techniques hereof may be practiced, thedata storage apparatus including a storage processor having multiplevirtualized storage processors (VSPs);

FIG. 2 is a block diagram showing example features of the front end ofFIG. 1 in additional detail;

FIG. 3 is a block diagram showing an example set of file systems of aVSP of FIG. 1;

FIG. 4 is a table showing an example set of records stored in aconfiguration database that defines a VSP that can be run on the storageprocessor of FIG. 1;

FIGS. 5A and 5B are block diagrams showing example arrangements ofvirtualized storage processors; and

FIG. 6 is a flowchart showing an example process for managing host datausing a VSP.

FIG. 7 is a block diagram illustrating particular details of areplication procedure which is performed by a data storage system when auser enters a single replication command into a user interface.

FIG. 8 is a flowchart of a procedure which is performed by the datastorage system to establish multiple replication sessions in response toa single replication command.

DETAILED DESCRIPTION

Overview

Embodiments of the invention will now be described. It is understoodthat such embodiments are provided by way of example to illustratevarious features and principles of the invention, and that the inventionhereof is broader than the specific example embodiments disclosed.

An improved technique is directed to automatically creating multiplereplication sessions in response to a single replication command enteredby a user. Such a command directs creation of a virtual storageprocessor (VSP) replication session to reliably and robustly replicate afile system environment, and further directs creation of standalone filesystem replication sessions to replicate separate user file systems. Inparticular, the necessary replication information for creating thereplication sessions can be derived automatically from records in aconfiguration database. Accordingly, the user is required to simplyenter one replication command regardless of the number of user filesystems being replicated and regardless of the data storage systemtopology. Therefore, there is little or no opportunity for error, andthe work of the user is less tedious and time consuming.

Data Storage System Details

Data storage systems typically include one or more physical storageprocessors (SPs) accessing an array of disk drives and/or electronicflash drives. Each SP is connected to a network, such as the Internetand/or a storage area network (SAN), and receives transmissions over thenetwork from host computing devices (“hosts”). The transmissions fromthe hosts include “IO requests,” also called “host IOs.” Some IOrequests direct the SP to read data from an array, whereas other IOrequests direct the SP to write data to the array. Also, some IOrequests perform block-based data requests, where data are specified byLUN (Logical Unit Number) and offset values, whereas others performfile-based requests, where data are specified using file names andpaths. Block-based IO requests typically conform to a block-basedprotocol, such as Fibre Channel or iSCSI (Internet SCSI, where SCSI isan acronym for Small Computer System Interface), for example. File-basedIO requests typically conform to a file-based protocol, such as NFS(Network File System), CIFS (Common Internet File System), or SMB(Server Message Block), for example.

In some data storage systems, an SP may operate one or more virtual datamovers. As is known, a virtual data mover is a logical grouping of filesystems and servers that is managed by the SP and provides a separatecontext for managing host data stored on the array. A single SP mayprovide multiple virtual data movers for different users or groups. Forexample, a first virtual data mover may organize data for users in afirst department of a company, whereas a second virtual data mover mayorganize data for users in a second department of the company. Eachvirtual data mover may include any number of host file systems forstoring user data.

In a typical virtual data mover arrangement, the SP has a root filesystem with mount points to which the host file systems of each virtualdata mover are mounted. Thus, the SP and all its virtual data moversform a single, large directory and all share a common namespace. Hostscan access their virtual data mover-managed data by connecting to the SPover the network, logging on, and specifying paths relative to the SP'sroot where their data are kept. The typical arrangement thus requireshosts to access data of a virtual data mover using paths that arereferenced to and dependent upon the root of the SP.

In addition, settings for prescribing virtual data mover operations areconventionally stored in the root file system of the SP. Many of thesesettings are global to all virtual data movers operating on the SP;others may be specific to particular virtual data movers.

Unfortunately, the intermingling of virtual data mover content within anSP's root file system impairs the ease of mobility and management ofvirtual data movers. For example, administrators wishing to move avirtual data mover (e.g., its file systems, settings, and servers) fromone SP to another SP must typically perform many steps on a varietydifferent data objects. File systems, server configurations, and othersettings may need to be moved one at a time. Also, as the contents ofdifferent virtual data movers are often co-located, care must be takento ensure that changes affecting one virtual data mover do not disruptthe operation of other virtual data movers.

In contrast with the conventional approach, an improved technique formanaging host data in a data storage apparatus provides virtualizedstorage processors (VSPs) as substantially self-describing andindependent entities. Each VSP has its own namespace, which isindependent of the namespace of any other VSP. Each VSP also has its ownnetwork address. Hosts may thus access VSPs directly, without having toinclude path information relative to the SP on which the VSPs areoperated. VSPs can thus be moved from one physical SP to another withlittle or no disruption to hosts, which may in many cases continue toaccess the VSPs on the new SPs using the same paths as were used toaccess the VSPs on the original SPs.

In some examples, each VSP includes within its namespace a configurationfile system storing configuration settings for operating the VSP. Theseconfiguration settings include, for example, network interface settingsand internal settings that describe the VSPs “personality,” i.e., themanner in which the VSP interacts on the network. By providing thesesettings as part of the VSP itself (e.g., within the file systems of theVSP), the VSP can be moved from one physical SP to another substantiallyas a unit. The increased independence of the VSP from its hosting SPpromotes many aspects of VSP management, including, for example,migration, replication, failover, trespass, multi-tenancy, loadbalancing, and gateway support.

In some examples, the independence of VSPs is further promoted bystoring data objects of VSPs in the form of respective files. These dataobjects may include, for example, file systems, LUNs, virtual storagevolumes (vVols), and virtual machine disks (VMDKs). Each such file ispart of a set of internal file systems of the data storage apparatus.Providing data objects in the form of files of a set of internal filesystems promotes independence of VSPs and unifies management offile-based objects and block-based objects.

In accordance with improvements hereof, certain embodiments are directedto a method of managing host data on a data storage apparatus connectedto a network. The method includes storing a network address and a set ofhost data objects accessible within a namespace of a virtualized storageprocessor (VSP) operated by a physical storage processor of the datastorage apparatus. The namespace includes only names of objects that arespecific to the VSP. The method further includes receiving, by thephysical storage processor, a transmission over the network from a hostcomputing device. The transmission is directed to a network address andincludes an IO request designating a pathname to a host data object tobe written or read. The method still further includes identifying thehost data object designated by the IO request by (i) matching thenetwork address to which the transmission is directed with the networkaddress stored for the VSP, to identify the VSP as the recipient of theIO request, and (ii) locating the host data object within the namespaceof the VSP using the pathname. The IO request is then processedprocessed to complete the requested read or write operation on theidentified host data object.

Other embodiments are directed to computerized apparatus and computerprogram products. Some embodiments involve activity that is performed ata single location, while other embodiments involve activity that isdistributed over a computerized environment (e.g., over a network).

An improved technique for managing host data in a data storage apparatusprovides virtualized storage processors (VSPs) as substantiallyself-describing and independent constructs.

FIG. 1 shows an example environment 100 in which embodiments of theimproved technique hereof can be practiced. Here, multiple hostcomputing devices (“hosts”) 110(1) through 110(N), access a data storageapparatus 116 over a network 114. The data storage apparatus 116includes a physical storage processor, or “SP,” 120 and storage 180. Thestorage 180 is provided, for example, in the form of hard disk drivesand/or electronic flash drives. Although not shown in FIG. 1, the datastorage apparatus 116 may include multiple SPs like the SP 120. Forinstance, multiple SPs may be provided as circuit board assemblies, or“blades,” which plug into a chassis that encloses and cools the SPs. Thechassis has a backplane for interconnecting the SPs, and additionalconnections may be made among SPs using cables. It is understood,however, that no particular hardware configuration is required, as anynumber of SPs (including a single one) can be provided and the SP 120can be any type of computing device capable of processing host IOs.

The network 114 can be any type of network, such as, for example, astorage area network (SAN), local area network (LAN), wide area network(WAN), the Internet, some other type of network, and/or any combinationthereof. In an example, the hosts 110(1-N) connect to the SP 120 usingvarious technologies, such as Fibre Channel, iSCSI, NFS, SMB 3.0, andCIFS, for example. Any number of hosts 110(1-N) may be provided, usingany of the above protocols, some subset thereof, or other protocolsbesides those shown. As is known, Fibre Channel and iSCSI areblock-based protocols, whereas NFS, SMB 3.0, and CIFS are file-basedprotocols. The SP 120 is configured to receive IO requests 112(1-N) intransmissions from the hosts 110(1-N) according to both block-based andfile-based protocols and to respond to such IO requests 112(1-N) byreading or writing the storage 180.

The SP 120 is seen to include one or more communication interfaces 122,control circuitry (e.g., a set of processors 124), and memory 130. Thecommunication interfaces 122 include, for example, adapters, such asSCSI target adapters and network interface adapters, for convertingelectronic and/or optical signals received from the network 114 toelectronic form for use by the SP 120. The set of processors 124includes one or more processing chips and/or assemblies. In a particularexample, the set of processors 124 includes numerous multi-core CPUs.The memory 130 includes both volatile memory (e.g., RAM), andnon-volatile memory, such as one or more ROMs, disk drives, solid statedrives (SSDs), and the like. The set of processors 124 and the memory130 are constructed and arranged to carry out various methods andfunctions as described herein. Also, the memory 130 includes a varietyof software constructs realized in the form of executable instructions.When the executable instructions are run by the set of processors 124,the set of processors 124 are caused to carry out the operations of thesoftware constructs. Although certain software constructs arespecifically shown and described, it is understood that the memory 130typically includes many other software constructs, which are not shown,such as various applications, processes, and daemons.

As shown, the memory 130 includes an operating system 134, such as Unix,Linux, or Windows™, for example. The operating system 134 includes akernel 136. The memory 130 is further seen to include a container 132.In an example, the container 132 is a software process that provides anisolated userspace execution context within the operating system 134. Invarious examples, the memory 130 may include multiple containers likethe container 132, with each container providing its own isolateduserspace instance. Although containers provide isolated environmentsthat do not directly interact (and thus promote fault containment),different containers can be run on the same kernel 136 and cancommunicate with one another using inter-process communication (IPC)mediated by the kernel 136. Containers are well-known features of Unix,Linux, and other operating systems.

In the example of FIG. 1, only a single container 132 is shown. Runningwithin the container 132 is an IO stack 140 and multiple virtualizedstorage processors (VSPs) 150(1-3). The IO stack 140 provides anexecution path for host IOs (e.g., 112(1-N)) and includes a front end142 and a back end 144. The VSPs 150(1-3) each run within the container132 and provide a separate context for managing host data. In anexample, each VSP manages a respective set of host file systems and/orother data objects and uses servers and settings for communicating overthe network 114 with its own individual network identity. Although threeVSPs are shown, it is understood that the SP 120 may include as few asone VSP or as many VSPs as the computing resources of the SP 120 andstorage resources of the storage 180 allow.

Although the VSPs 150(1-3) each present an independent and distinctidentity, it is evident that the VSPs 150(1-3) are not, in this example,implemented as independent virtual machines. Rather, all VSPs 150(1-3)operate in userspace and employ the same kernel 136 of the SP 120.Although it is possible to implement the VSPs 150(1-3) as independentvirtual machines (each including a virtualized kernel), it has beenobserved that VSPs perform faster when the kernel 136 is notvirtualized.

Also, it is observed that the VSPs 150(1-3) all run within the container132, i.e., within a single userspace instance. Again, the arrangementshown reflects a deliberate design choice aimed at optimizing VSPperformance. It is understood, though, that alternative implementationscould provide different VSPs in different containers, or could beprovided without containers at all.

The memory 130 is further seen to store a configuration database 170.The configuration database 170 stores system configuration information,including settings related to the VSPs 150(1-3) and their data objects.In other implementations, the configuration database 170 is storedelsewhere in the data storage apparatus 116, such as on a disk driveseparate from the SP 120 but accessible to the SP 120, e.g., over abackplane or network.

In operation, the hosts 110(1-N) issue IO requests 112(1-N) to the datastorage apparatus 116. The IO requests 112(1-N) may include bothblock-based requests and file-based requests. The SP 120 receives the IOrequests 112(1-N) at the communication interfaces 122 and passes the IOrequests to the IO stack 140 for further processing.

At the front end 142 of the IO stack 140, processing includesassociating each of the IO requests 112(1-N) with a particular one ofthe VSPs 150(1-3). In an example, each VSP stores a network address(e.g., an IP address) in a designated location within its file systems.The front end 142 identifies the network address to which each IOrequest is directed and matches that address with one of the networkaddresses stored with the VSPs 150(1-3). The front end 142 thus uses thenetwork address to which each IO request is sent to identify the VSP towhich the IO request is directed. Further processing of the IO requestis then associated (e.g., tagged) with an identifier of the matchingVSP, such that the IO request is processed within a particular VSPcontext. Any data logging, metrics collection, fault reporting, ormessages generated while the IO request is being processed are storedwith the associated VSP (e.g., in a file system dedicated to the VSP).Also, any path information provided with the IO request (e.g., to aparticular directory and file name) is interpreted within the namespaceof the identified VSP.

Processing within the front end 142 may further include caching dataprovided with any write IOs and mapping host data objects (e.g., hostfile systems, LUNs, vVols, VMDKs, etc.) to underlying files stored in aset of internal file systems. Host IO requests received for reading andwriting both file systems and LUNs are thus converted to reads andwrites of respective files. The IO requests then propagate to the backend 144, where commands are executed for reading and/or writing thephysical storage 180.

In an example, processing through the IO stack 140 is performed by a setof threads maintained by the SP 120 in a set of thread pools. When an IOrequest is received, a thread is selected from the set of thread pools.The IO request is tagged with a VSP identifier, and the selected threadruns with the context of the identified VSP. Typically, multiple threadsfrom different thread pools contribute to the processing of each IOrequest (there are many processing layers). Multiple threads from thethread pools can process multiple IO requests simultaneously, i.e., inparallel, on the data objects of any one VSP or multiple VSPs.

Although FIG. 1 shows the front end 142 and the back end 144 together inan “integrated” form, the front end 142 and back end 144 mayalternatively be provided on separate SPs. For example, the IO stack 140may be implemented in a “modular” arrangement, with the front end 142 onone SP and the back end 144 on another SP. The IO stack 140 may furtherbe implemented in a “gateway” arrangement, with multiple SPs runningrespective front ends 142 and with a back end provided within a separatestorage array. The back end 144 performs processing that is similar toprocessing natively included in many block-based storage arrays.Multiple front ends 142 can thus connect to such arrays without the needfor providing separate back ends. In all arrangements, processingthrough both the front end 142 and back end 144 is preferably taggedwith the particular VSP context such that the processing remainsVSP-aware.

FIG. 2 shows portions of the front end 142 in additional detail. Here,and describing the architecture generally without regard to anyparticular VSP, it is seen that a set of lower-deck file systems 202represents LUNs and host file systems in the form of files. Any numberof lower-deck file systems 202 may be provided. In one arrangement, asingle lower-deck file system may include, as files, any number of LUNsand/or host file systems, as well as their snaps (i.e., point-in-timecopies). In another arrangement, a different lower-deck file system isprovided for each primary object to be stored, e.g., for each LUN andfor each host file system. Additional arrangements provide groups ofhost file systems and/or groups of LUNs together in a single lower deckfile system. The lower-deck file system for any object may include afile storing the object itself, as well as files storing any snaps ofthe object. Each lower-deck file system 202 has an inode table (e.g.,232, 242), which provides a unique inode for each file stored in thelower-deck file system. The inode table of each lower-deck file systemstores properties of each file in the respective lower-deck file system,such as ownership and block locations at which the file's data arestored. Lower-deck file systems are built upon storage elements managedby a storage pool 204.

The storage pool 204 organizes elements of the storage 180 in the formof slices. A “slice” is an increment of storage space, such as 256 MB insize, which is obtained from the storage 180. The pool 204 may allocateslices to lower-deck file systems 202 for use in storing their files.The pool 204 may also deallocate slices from lower-deck file systems 202if the storage provided by the slices is no longer required. In anexample, the storage pool 204 creates slices by accessing RAID groupsformed from the storage 180, dividing the RAID groups into FLUs (FlareLUNs), and further dividing the FLU's into slices.

Continuing with reference to the example shown in FIG. 2, a user objectlayer 206 includes a representation of a LUN 210 and of an HFS (hostfile system) 212, and a mapping layer 208 includes a LUN-to-file mapping220 and an HFS-to-file mapping 222. The LUN-to-file mapping 220 maps theLUN 210 to a first file F1 (236), and the HFS-to-file mapping 222 mapsthe HFS 212 to a second file F2 (246). Through the LUN-to-file mapping220, any set of blocks identified in the LUN 210 by a host IO request ismapped to a corresponding set of blocks within the first file 236.Similarly, through the HFS-to-file mapping 222, any file or directory ofthe HFS 212 is mapped to a corresponding set of blocks within the secondfile 246. The HFS 212 is also referred to herein as an “upper-deck filesystem,” which is distinguished from the lower-deck file systems 202,which are for internal use.

In this example, a first lower-deck file system 230 includes the firstfile 236 and a second lower-deck file system 240 includes the secondfile 246. Each of the lower-deck file systems 230 and 240 includes aninode table (232 and 242, respectively). The inode tables 232 and 242provide information about files in respective lower-deck file systems inthe form of inodes. For example, the inode table 232 of the firstlower-deck file system 230 includes an inode 234, which providesfile-specific information about the first file 236. Similarly, the inodetable 242 of the second lower-deck file system 240 includes an inode244, which provides file-specific information about the second file 246.The information stored in each inode includes location information(e.g., block locations) where the respective file is stored, and maythus be accessed as metadata to identify the locations of the files 236and 246 in the storage 180.

Although a single file is shown for each of the lower-deck file systems230 and 240, it is understood that each of the lower-deck file systems230 and 240 may include any number of files, each with its own entry inthe respective inode table. In one example, each lower-deck file systemstores not only the file F1 or F2 for the LUN 210 or HFS 212, but alsosnaps of those objects. For instance, the first lower-deck file system230 stores the first file 236 along with a different file for every snapof the LUN 210. Similarly, the second lower-deck file system 240 storesthe second file 246 along with a different file for every snap of theHFS 212.

As shown, a set of slices 260 is allocated by the storage pool 204 forstoring the first file 236 and the second file 246. In the exampleshown, slices S1 through S4 are used for storing the first file 236, andslices S5 through S7 are used for storing the second file 246. The datathat make up the LUN 210 are thus stored in the slices S1 through S4,whereas the data that make up the HFS 212 are stored in the slices S5through S7.

In some examples, each of the lower-deck file systems 230 and 240 isassociated with a respective volume, such as a sparse LUN. Sparse LUNsprovide an additional layer of mapping between the lower-deck filesystems 202 and the pool 204 and allow the lower-deck file systems tooperate as file systems normally do, by accessing underlying volumes.Additional details about sparse LUNs and their relation to lower-deckfile systems may be found in U.S. Pat. No. 7,631,155, which is herebyincorporated by reference in its entirety. The incorporated patent usesthe term “container file system” to refer to a construct similar to thelower-deck file system disclosed herein.

Although the example of FIG. 2 shows storage of a LUN 210 and a hostfile system 212 in respective lower-deck file systems 230 and 240, it isunderstood that other data objects may be stored in one or morelower-deck file systems in a similar manner. These may include, forexample, file-based vVols, block-based vVols, and VMDKs.

FIG. 3 shows an example set of components of the data storage apparatus116 that are associated with a particular VSP 300 (i.e., any of the VSPs150(1-3)). The components shown in FIG. 3 include components that aremanaged in the context of the VSP 300 and components that form the“personality” of the VSP 300. These components may be referred to hereinas “included” within the VSP 300, by which it is meant that thecomponents are associated with the VSP 300 within the data storageapparatus 116 and are not associated with any other VSP. It is thus seenthat the VSP 300 “includes” a number of lower-deck file systems hostingvarious host data objects, as well as internal data objects.

For example, the VSP 300 includes a first lower-deck file system 310 anda second lower-deck file system 320. The first lower-deck file system310 includes a file FA, which provides a file representation of a firsthost file system 312. Similarly, the second lower-deck file system 320includes a file FB, which provides a file representation of a secondhost file system 322. The host file systems 312 and 322 are upper-deckfile systems, which may be made available to hosts 110(1-N) for storingfile-based host data. HFS-to-file mappings, like the HFS-to-file mapping222, are understood to be present (although not shown in FIG. 3) forexpressing the files FA and FB in the form of upper-deck file systems.Although only two host file systems 312 and 322 are shown, it isunderstood that the VSP 300 may include any number of host file systems.In an example, a different lower-deck file system is provided for eachhost file system. The lower-deck file system stores the filerepresentation of the host file system, and, if snaps are turned on, anysnaps of the host file system. In a similar manner to that described inconnection with FIG. 2, each of the lower-deck file systems 310 and 320includes a respective inode table, allowing the files FA and FB andtheir snaps to be indexed within the respective lower-deck file systemsand accessed within the storage 180.

In some examples, the VSP 300 also includes one or more lower-deck filesystems for storing file representations of LUNs. For example, alower-deck file system 330 stores a file FC, which provides a filerepresentation of a LUN 332. A LUN-to-file mapping (not shown butsimilar to the mapping 320) expresses the file FC in the form of a LUN,which may be made available to hosts 110(1-N) for storing block-basedhost data. In an example, the lower-deck file system 330 stores not onlythe file FC, but also snaps thereof, and includes an inode table inessentially the manner described above.

The VSP 300 further also includes a lower-deck file system 340. In anexample, the lower-deck file system 340 stores file representations FDand FE of two internal file systems of the VSP 300—a root file system342 and a configuration file system 344. In an alternative arrangement,the files FD and FE are provided in different lower-deck file systems.In an example, the lower-deck file system 340 also stores snaps of thefiles FD and FE, and files are accessed within the lower-deck filesystem 340 via file system-to-file mappings and using an inode table,substantially as described above.

In an example, the root file system 342 has a root directory, designatedwith the slash (“/”), and sub-directories as indicated. Any number ofsub-directories may be provided within the root file system in anysuitable arrangement with any suitable file structure; the example shownis merely illustrative. As indicated, one sub-directory (“Local”)stores, for example, within constituent files, information about thelocal environment of the SP, such as local IP sub-net information,geographical location, and so forth. Another sub-directory (“Rep”)stores replication information, such as information related to anyongoing replication sessions. Another sub-directory (“Cmd Svc”) storescommand service information, and yet another sub-directory (“MPs”)stores mount points.

In the example shown, the directory “MPs” of the root file system 342provides mount points (e.g., directories) on which file systems aremounted. For example, the host file systems 312 and 322 are respectivelymounted on mount points MP1 and MP2, and the configuration file system344 is mounted on the mount point MP3. In an example, establishment ofthe mount points MP1-MP3 and execution of the mounting operations formounting the file systems 312, 322, 344 onto the mount points MP1-MP4are provided in a batch file stored in the configuration file system 344(e.g., in Host Objects). It is understood that additional mount pointsmay be provided for accommodating additional file systems.

The root file system 342 has a namespace, which includes the names ofthe root directory, sub-directories, and files that belong to the rootfile system 342. The file systems 312, 322, and 344 also each haverespective namespaces. The act of mounting the file systems 312, 322,and 344 onto the mount points MP1, MP2, and MP3 of the root file system342 serves to join the namespace of each of the file systems 312, 322,and 344 with the namespace of the root file system 342, to form a singlenamespace that encompasses all the file systems 312, 322, 342, and 344.This namespace is specific to the VSP 300 and is independent ofnamespaces of any other VSPs.

Also, it is understood that the LUN 332 is also made available to hosts110 a-n through the VSP 300. For example, hosts 110 a-n can send readand write IO requests to the LUN 332 (e.g., via Fibre Channel and/oriSCSI commands) and the SP 120 services the requests for the VSP 300,e.g., by operating threads tagged with the context of the VSP 300.Although FIG. 3 shows both the LUN 322 and the host file systems 312 and322 together in a single VSP 300, other examples may provide separateVSPs for LUNs and for file systems.

Although the VSP 300 is seen to include file systems and LUNs, otherhost objects may be included, as well. These include, for example,file-based vVols, block-based vVols, and VMDKs. Such host objects may beprovided as file representations in lower-deck file systems and madeavailable to hosts 110 a-n.

As its name suggests, the configuration file system 344 storesconfiguration settings for the VSP 300. These settings include settingsfor establishing the “personality” of the VSP 300, i.e., the manner inwhich the VSP 300 interacts over the network 114. Although theconfiguration file system 344 is shown with a particular directorystructure, it is understood that any suitable directory structure can beused. In an example, the configuration file system 344 stores thefollowing elements:

-   -   IF Config. Interface configuration settings of any network        interface used for processing IO requests and tagged with a        context of the VSP 300. IF Config includes the IP address of the        VSP, as well as related network information, such as sub-masks        and related IP information.    -   CIFS. Configuration settings and names of one or more CIFS        servers used in the context of the VSP 300. The CIFS servers        manage IO requests provided in the CIFS protocol. By including        the CIFS configuration within the configuration file system 344,        the CIFS configuration becomes part of the VSP 300 itself and        remains with the VSP 300 even as the VSP 300 is moved from one        SP to another SP. This per-VSP configuration of CIFS also        permits each VSP to have its own customized CIFS settings, which        may be different from the settings of CIFS servers used by other        VSPs.    -   NFS. Configuration settings and names of one or more NFS servers        used in the context of the VSP 300. The NFS servers manage IO        requests provided in the NFS protocol. By including the NFS        configuration within the configuration file system 344, the NFS        configuration becomes part of the VSP 300 itself and remains        with the VSP 300 even as the VSP 300 is moved from one SP to        another SP. This per-VSP configuration of NFS also permits each        VSP to have its own customized NFS settings, which may be        different from the settings of NFS servers used by other VSPs.    -   Exports. NFS exports, CIFS shares, and the like for all        supported protocols. For security and management of host access,        users are typically given access only to specified resources        mounted to the root file system 342, e.g., host file systems,        sub-directories of those file systems, and/or particular LUNs.        Access to these resources is provided by performing explicit        export/share operations, which expose entry points to the        resources for host access. In an example, these export/share        operations are included within one or more batch files, which        may be executed when the VSP 300 is started. Exports are        typically VSP-specific, and depend upon the particular data        being hosted and the access required.    -   CAVA/NDMP: CAVA (Celerra Anti-Virus Agent) configuration file,        including location of external server for performing virus        checking operations. NDMP (Network Data Management Protocol)        provides backup configuration information. CAVA and NDMP        settings are configurable on a per-VSP basis.    -   NIS/DNS/LDAP: Local configurations and locations of external        servers for providing resolution of IP addresses. NIS (Network        Information Service), DNS (Directory Name System), and LDAP        (Lightweight Directory Access Protocol) settings are        configurable on a per-VSP basis. The DNS configuration stores        local host name and domain name of the VSP 300, as well as the        location of a DNS server for resolving host names.    -   Host Objects: Identifiers for all host file systems (e.g., 312        and 322), LUNs (e.g., LUN 332), and other host objects included        within the VSP 300. Host objects may also include batch files        and/or lists of instructions for establishing mount points in        the root file system 342 and for mounting the host file        system(s) and LUN(s) to the mount points.    -   Parameters: Low-level settings (e.g., registry settings) for        configuring VSP 300. These include cache settings and settings        for specifying a maximum number of threads running on the SP 120        that may be used to service IO requests within the context of        the VSP 300. Parameters are configurable on a per-VSP basis.    -   Statistics: Metrics, log files, and other information pertaining        to activities within the context of the VSP 300. Statistics are        updated as they accumulate.        Many configuration settings are established at startup of the        VSP 300. Some configuration settings are updated as the VSP 300        is operated. The configuration file system 344 preferably does        not store host data.

Although FIG. 3 has been shown and described with reference to aparticular VSP 300, it is understood that all of the VSPs 150(1-3) mayinclude a root file system, a configuration file system, and at leastone host file system or LUN, substantially as shown. Particular hostobjects and configuration settings differ, however, from one VSP toanother.

By storing the configuration settings of VSPs within the file systems ofthe VSPs themselves and providing a unique namespace for each VSP, VSPsare made to be highly independent, both of other VSPs and of theparticular SPs on which they are provided. For example, migrating a VSPfrom a first data storage system to a second data storage systeminvolves copying its lower-deck file systems (or some subset thereof)from a source SP on the first data storage system to a target SP on thesecond, starting the VSP's servers on the target SP in accordance withthe configuration settings, and resuming operation on the target SP. Asthe paths for accessing data objects on VSPs are not rooted to the SPson which they are run, hosts may often continue to access migrated VSPsusing the same instructions as were used prior to moving the VSPs.Similar benefits can be enjoyed when moving a VSP from one SP to anotherSP in the same data storage system. To move a VSP from a first SP to asecond SP, The VSP need merely be shut down (i.e., have its serversstopped) on the first SP and resumed (i.e., have its servers started upagain) on the second SP.

FIG. 4 shows an example record 400 of the configuration database 170,which are used to define a particular VSP having a VSP identifier (ID)410. The VSP ID 410 may identify one of the VSPs 150(1-3) or some otherVSP of the data storage apparatus 116. The record 400 specifies, forexample, an owning SP (physical storage processor), authentication, andidentifiers of the data objects associated with the listed VSP. The dataobject identifiers include identifiers of the root file system,configuration file system, and various host file systems (or other hostobjects) that may be accessed in the context of the listed VSP. Therecord 400 may also identify the lower-deck file system used to storeeach data object. The record 400 may further specify host interfacesthat specify IO protocols that the listed VSP is equipped to handle.

Although FIG. 4 shows only a single record 400 for a single VSP, it isunderstood that the configuration database 170 may store records, likethe record 400, for any number of VSPs, including all VSPs of the datastorage apparatus 116. During start-up of the data storage apparatus116, or at some other time, a computing device of the data storageapparatus 116 reads the configuration database 170 and launches aparticular VSP or a group of VSPs on the identified SPs. As a VSP isstarting, the SP that owns the VSP reads the configuration settings ofthe configuration file system 344 to configure the various servers ofthe VSP and to initialize its communication protocols. The VSP may thenbe operated on the identified SP, i.e., the SP may then be operated withthe particular VSP's context.

It is understood that VSPs 150(1-3) operate in connection with the frontend 142 of the IO stack 140. The VSPs 150(1-3) thus remain co-locatedwith their respective front ends 142 in modular and gatewayarrangements.

FIGS. 5A and 5B show two different example arrangements of VSPs. In FIG.5A, the VSPs 150(1-3) access the storage pool 204. Thus, the lower-deckfile systems of the VSPs 150(1-3) all derive the slices needed to storetheir underlying file systems and other data objects from the pool 204.In FIG. 5B, multiple storage pools 550(1-3) are provided, one for eachof the VSPs 150(1-3), respectively. Providing different pools forrespective VSPs promotes data isolation among the VSPs, and may bebetter suited for applications involving multiple tenants in which eachtenant's data must be kept separate from the data of other tenants.

FIG. 6 shows an example method 600 for managing host data on a datastorage apparatus connected to a network. The method 600 that may becarried out in connection with the data storage apparatus 116. Themethod 600 is typically performed by the software constructs, describedin connection with FIGS. 1-3, which reside in the memory 130 of thestorage processor 120 and are run by the set of processors 124. Thevarious acts of the method 600 may be ordered in any suitable way.Accordingly, embodiments may be constructed in which acts are performedin orders different from those illustrated, which may include performingsome acts simultaneously, even though the acts are shown as sequentialin the illustrated embodiments.

At step 610, a network address and a set of host data objects are storedin a data storage apparatus. The set of host data objects are accessiblewithin a namespace of a virtualized storage processor (VSP) operated bya physical storage processor of the data storage apparatus. Thenamespace includes only names of objects that are specific to the VSP.For example, an IP address of the VSP 300 is stored in a file of adirectory of the configuration file system 344. The VSP 300 runs on theSP 120 of the data storage apparatus 116. A set of host objects,including host file systems 312 and 322, and LUN 332, are also stored inthe data storage apparatus 116. These host objects are made accessiblewithin the namespace of the VSP 300 by mounting these data objects tomount points MP1-MP4 within the root file system 342 and thus mergingtheir namespaces with that of the root file system 342. The resultingmerged namespace includes only names of objects that are specific to theVSP 300.

At step 612, a transmission is received by the physical storageprocessor over the network from a host computing device. Thetransmission is directed to a network address and includes an IO requestdesignating a pathname to a host data object to be written or read. Forexample, the SP 120 receives a transmission over the network 114 fromone of the hosts 110(1-N). The transmission is directed to a particularIP address and includes an IO request (e.g., one of 112(1-N)). The IOrequest designates a location of a host data object to be written orread (e.g., a pathname for a file-based object or a block designationfor a block-based object). The location may point to any of the hostfile systems 312 or 322, to the LUN 332, or to any file or offset rangeaccessible through the host file systems 312 or 322 or the LUN 332,respectively. The location may also point to a vVol or VMDK, forexample, or to any other object which is part of the namespace of theVSP 300.

At step 614, the host data object designated by the IO request isidentified by (i) matching the network address to which the transmissionis directed with the network address stored for the VSP, to identify theVSP as the recipient of the IO request, and (ii) locating the host dataobject within the namespace of the VSP using the pathname. For example,each of the VSPs 150(1-3) stores an IP address in its configuration filesystem 344. When an IO request is received, an interface running withinthe front end 142 of the IO stack 140 checks the IP address to which theIO request is directed and matches that IP address with one of the IPaddresses stored for the VSPs 150(1-3). The VSP whose IP address matchesthe IP address to which the IO request is directed is identified as therecipient of the IO request. The IO request arrives to the SP 120 with apathname to the host data object to be accessed. The front end 142 looksup the designated pathname within the identified VSP to identify theparticular data object to which the IO request is directed.

At step 616, the IO request is processed to complete the requested reador write operation on the identified host data object. For example, thefront end 142 and the back end 144 process the IO request to perform anactual read or write to the designated host data object on the storage180.

An improved technique has been described for managing host data in adata storage apparatus. The technique provides virtualized storageprocessors (VSPs) as substantially self-describing and independententities. Each VSP has its own namespace, which is independent of thenamespace of any other VSP. Each VSP also has its own network address.Hosts may thus access VSPs directly, without having to include pathinformation relative to the SP on which the VSP is operated. VSPs canthus be moved from one physical SP to another with little or nodisruption to hosts, which may continue to access the VSPs on the newSPs using the same paths as were used when the VSPs were running on theoriginal SPs.

As used throughout this document, the words “comprising,” “including,”and “having” are intended to set forth certain items, steps, elements,or aspects in an open-ended fashion. Also, and unless explicitlyindicated to the contrary, the word “set” as used herein indicates oneor more of something. Although certain embodiments are disclosed herein,it is understood that these are provided by way of example only and theinvention is not limited to these particular embodiments.

Having described certain embodiments, numerous alternative embodimentsor variations can be made. For example, embodiments have been shown anddescribed in which host file systems, LUNs, vVols, VMDKs, and the likeare provided in the form of files of underlying lower-deck file systems.Although this arrangement provides advantages for simplifying managementof VSPs and for unifying block-based and file-based operations, the useof lower-deck file systems is merely an example. Indeed, host filesystems, LUNs, vVols, VMDKs, and the like may be provided for VSPs inany suitable way.

Also, although the VSPs 150(1-3) are shown and described as userspaceconstructs that run within the container 132, this is also merely anexample. Alternatively, different VSPs may be provided in separatevirtual machines running on the SP 120. For example, the SP 120 isequipped with a hypervisor and a virtual memory manager, and each VSPruns in a virtual machine having a virtualized operating system.

Also, the improvements or portions thereof may be embodied as anon-transient computer-readable storage medium, such as a magnetic disk,magnetic tape, compact disk, DVD, optical disk, flash memory,Application Specific Integrated Circuit (ASIC), Field Programmable GateArray (FPGA), and the like (shown by way of example as medium 650 inFIG. 6). Multiple computer-readable media may be used. The medium (ormedia) may be encoded with instructions which, when executed on one ormore computers or other processors, implement the various methodsdescribed herein. Such medium (or media) may be considered an article ofmanufacture or a machine, and may be transportable from one machine toanother.

Replication Details

FIG. 7 shows particular details of a replication procedure which isperformed by a data storage system 800 when a user enters a singlereplication command into a user interface. Although certain data storageapparatus details are purposefully omitted from FIG. 7 for simplicity(also see FIG. 1), it should be understood that the data storage system800 includes a source site data storage apparatus 116(A), a destinationsite data storage apparatus 116(B), and a communications medium 802(e.g., a wide area network or WAN) through which the apparatus 116(A),116(B) communicate. It should be further understood that the user mayenter commands into the data storage system 800 via a control console orterminal (e.g., a user interface at either site) by simply typing into acommand line interface, operating a pointing device via a specializedgraphical user interface (GUI), and so on.

Initially and by way of example, suppose that the configuration database170 of the source site data storage apparatus 116(A) includes aparticular database record 400 for a particular VSP (also see FIGS. 1and 4). The particular VSP defined by the particular database record 400has a root file system “/” and appropriate mount points on which tomount other file systems.

Further suppose that the particular database record 400 (and/or otherrecords 400 of the configuration database 170) define other file systemswhich are mounted to the root file system of the particular VSP. In thisexample and as shown in FIG. 7 (see dashed lines), a VSP configurationfile system “/VSP Config” and two user file systems “/FS1”, “/FS2” aremounted to the root file system of the particular VSP.

As described earlier in connection with FIG. 3, the VSP configurationfile system “/VSP Config” includes VSP configuration data which definesan operating environment for the particular VSP (e.g., a networkaddress, CIFS settings, NFS settings, and so on). Accordingly, thepersonality or identity of the particular VSP is defined by the VSPconfiguration data in the VSP configuration file system.

The user file systems “/FS1”, “/FS2” include host data provided by hostapplications. Since the VSP configuration file system “/VSP Config”defines the operating environment for the user file systems “/FS1”,“/FS2”, accessibility of any replicas of the user file systems “/FS1”,“/FS2” requires presence of the VSP configuration file system “/VSPConfig”.

Now, suppose that a user (e.g., an administrator of the data storagesystem 800) wishes to replicate the particular VSP and the file systemswhich are mounted to the particular VSP to the destination site datastorage apparatus 116(B). Prior to starting replication, the user mayhave created an interconnect between the source site data storageapparatus 116(A) and the destination site data storage apparatus 116(B)(i.e., a secure and reliable communications pathway). Additionally, theroot file system “/” of the particular VSP may have already beencreated, and the user may have already mounted the various files systemsto the root file system. Accordingly, records 400 in the configurationdatabase 170 have been updated to reflect this activity.

At this point, the user is ready to simply enter a single replicationcommand. That is, rather than separately enter replication commands tobegin replication sessions for each file system as in a conventionalapproach, all the user needs to do is enter one replication command toeffectuate such replication. Additionally, the entire lifecycle of areplication session (i.e., create, delete, reverse, switchover, modify,failover, stop, start, etc.) which otherwise applies at the file systemlevel now applies at the VSP level. Furthermore, replication of theinternals of the VSP (e.g., the root, the VSP configuration data, etc.)are entirely hidden from the end user who simply manages the replicationsession. A suitable syntax for such a single replication command is:

$ nas_replicate -create_all -source src_VSP -destination dest_VSP

where “nas_replicate” is the specific instruction, “-create_all” is anoption directing replication of all mounted file systems, “-sourcesrc_VSP” is an option identifying the particular VSP (“src_VSP”) of thesource site data storage apparatus 116(A), and “-destination dest_VSP”is an option identifying a corresponding VSP (“dest_VSP”) to be createdon the destination site data storage apparatus 116(B). Other options canbe included as well such as an option that identifies a particularpre-established interconnect by name, another option that specifies amaximum time in which the VSPs can be out of sync (e.g., 30 seconds, oneminute, etc.), and so on.

In response to the single replication command, the processing circuitry124 of the source site data storage apparatus 116(A) accesses theconfiguration database 170 to identify which file systems are mounted tothe root file system of the particular VSP. In the context of a set ofprocessors executing software, it should be understood that executablecode for carrying out automated creation of multiple replicationsessions may reside in the front end 142 of the IO stack 140 (also seeFIG. 1).

In this example, the processing circuitry 124 sees that there are atleast three files systems (i.e., the VSP configuration file system andtwo user files systems) that are mounted to the root file system of theparticular VSP which are to be replicated. Accordingly, the processingcircuitry 124 automatically creates multiple replications sessions 804to replicate the mounted file systems.

In particular, the processing circuitry 124 makes sure that acorresponding root file system “/” exists on the data storage apparatus116(B) at the destination site and, if not, directs the data storageapparatus 116(B) to create a corresponding root file system “/”. Theprocessing circuitry 124 then creates a VSP configuration file systemreplication session 804(C) to replicate the VSP configuration filesystem. Additionally, the processing circuitry 124 creates user filesystem replication sessions 804(FS1), 804(FS2) to replicate the userfile systems FS1, FS2. Each replication session 804 properly mounts arespective file system to the root file system “/” of the data storageapparatus 116(B) and begins file system replication (e.g., synchronousreplication, asynchronous replication, snap, etc.). It should beunderstood that each replication session 804 is independent and operatesin a standalone manner with respect to the other replication sessions804.

With replication of the VSP configuration file system in place, theoperating environment at the destination site is now established toenable reliable and robust access to the user files system via thedestination data storage apparatus 116(B), e.g., read only access whilethe source data storage apparatus 116(A) operates as the source site.

However, in response to a failover event in which replication of a userfile system is stopped, the circuitry of the destination data storageapparatus 116(B) transitions that user file system at the destinationdata storage apparatus 116(B) from a host read-only state to a hostread/write state. Such operation enables read/write access to continueat the destination data storage apparatus 116(B) while other replicationsessions of the multiple replication sessions continue to operate intheir original states.

At this point, it should be understood that various other replicationrelated operations are suitable for use in combination with theabove-described VSP replication activities. For example, theautomatically created replication sessions 804 can be stopped, started,reversed, switched over, deleted, and so on. Furthermore, such sessions804 can be controlled in the aggregate (together as a group), orindividually, in response to other user commands.

FIG. 8 is a flowchart of a procedure 850 which is performed by the datastorage system 800 to perform replication. At 852, the processingcircuitry of the data storage system 800 receives a VSP replicationcommand from a user. The VSP replication command specifies a source VSPand a destination VSP.

At 854, in response to the VSP replication command, the processingcircuitry identifies multiple source data objects which are configuredto store data from the context of the source VSP (e.g., the source dataobjects store data using an operating environment which is defined bythe source VSP). Along these lines, the configuration database 170stores a set of records 400 which indicates which file systems aremounted to the root file system of the source VSP, and among the filessystems is a configuration file system storing VSP configuration data(i.e., VSP “personality” information, also see FIG. 3). Recall that thedata objects may be lower-deck files 236, 246 of lower-deck file systems202 containing, as the user file systems, upper-deck file systems formedof upper-deck files (also see FIG. 2).

At 856, after the multiple source data objects are identified, theprocessing circuitry automatically creates multiple replication sessions804 to replicate the multiple source data objects as multipledestination data objects which are configured to store data from thecontext of the destination VSP. During these replication sessions, blockchanges are conveyed from source site to the destination site throughthe communications medium 802 (e.g., a WAN).

As described above, improved techniques are directed to automaticallycreating multiple replication sessions 804 in response to a singlereplication command from a user. Such a command directs creation of aVSP replication session 804(C) to reliably and robustly replicate a filesystem environment, and further directs creation of standalone filesystem replication sessions 804(FS1), 804(FS2), . . . to replicateseparate user file systems FS1, FS2, . . . . Along these lines, thenecessary replication information for creating the replication sessionscan be derived in an automated manner from records in a configurationdatabase 170. Accordingly, the user is required to simply enter onereplication command regardless of the number of user file systems beingreplicated and the data storage system topology. As a result, there islittle or no opportunity for error, and the work of the user is lesstedious and time consuming.

While various embodiments of the present disclosure have beenparticularly shown and described, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims.

For example, it should be understood that the above-described techniquesare suitable for complex topologies such as one-to-many configurationsand cascade configurations. For such topologies, a single replicationcommand from the user may establish many replications sessions 804automatically, e.g., 10, 50, more than 100, etc.

Additionally, it should be understood that the above-describedreplication techniques are appropriate for synchronous replication,asynchronous replication, snapshots, copy sessions, and so on. Moreover,the above-described replication techniques do not preclude the datastorage system 800 from offering the ability to create sessionsindividually. Rather, such techniques are available to the user whenappropriate and may be used in combination with conventional approaches.

Furthermore, the above-described replication command was described aboveas being entered by a user by way of example only. In otherarrangements, the replication command is can be called automatically,e.g., via a script, from a program as part of an application programminginterface (API), and so on.

Additionally, it should be understood that data within a VSPconfiguration file system of a VSP on the source side may be overwrittenat session failover time with data from a VSP configuration file systemof a VSP on the destination side. Such an operation may occur, forinstance, when the network configuration on the destination side was notcompatible with that of the source side and had to be modified. Suchmodifications and enhancements are intended to belong to variousembodiments of the disclosure.

Further, although features are shown and described with reference toparticular embodiments hereof, such features may be included in any ofthe disclosed embodiments and their variants. Thus, it is understoodthat features disclosed in connection with any embodiment can beincluded as variants of any other embodiment, whether such inclusion ismade explicit herein or not. Those skilled in the art will thereforeunderstand that various changes in form and detail may be made to theembodiments disclosed herein without departing from the scope of thedisclosure.

What is claimed is:
 1. A method of performing replication, the methodcomprising: receiving, by processing circuitry, a virtual storageprocessor (VSP) replication command from a user, the VSP replicationcommand specifying a source VSP and a destination VSP; identifying, bythe processing circuitry and in response to the VSP replication command,multiple source data objects which are configured to store data from thecontext of the source VSP; and after the multiple source data objectsare identified, automatically creating multiple replication sessions toreplicate the multiple source data objects as multiple destination dataobjects which are configured to store data from the context of thedestination VSP, wherein a configuration database holds multiple VSPrecords corresponding to multiple VSPs, wherein identifying the multiplesource data objects includes (i) locating, from the configurationdatabase, a set of VSP records corresponding to the source VSP and (ii)ascertaining, from the set of VSP records, the multiple source dataobjects which are configured to store data from the context of thesource VSP, wherein the multiple source data objects which areconfigured to store data from the context of the source VSP includemultiple file systems, wherein the set of VSP records corresponding tothe source VSP includes an identifier of each of the multiple filesystems and a set of host interfaces through which the multiple filesystems are accessed, wherein ascertaining the multiple source dataobjects includes constructing a list of lower-deck files from the set ofVSP records, each lower-deck file on the list being one of the multiplesource data objects, wherein at least some lower-deck files containupper-deck file systems of upper-deck files; and wherein the methodfurther comprises, prior to creating the multiple replication sessions,mounting the upper-deck file systems to a root file system of the sourceVSP.
 2. A method as in claim 1 wherein a VSP configuration file systemis contained within a particular lower-deck file, the VSP configurationfile system having VSP configuration files which store VSP configurationdata; and wherein creating the multiple replication sessions includes:establishing a VSP configuration file system replication session toreplicate the VSP configuration file system to the destination VSP.
 3. Amethod as in claim 1 wherein a set of user file systems is containedwithin a set of lower-deck files, the set of user files systems havinguser files which store host data; and wherein creating the multiplereplication sessions further includes: establishing a set of user filesystem replication sessions to replicate the set of user file systems tothe destination VSP, each user file system replication session being astandalone session which is independent of the other user file systemreplication sessions.
 4. A method as in claim 1, further comprising: inresponse to host input/output (I/O) requests and during the multiplereplication sessions, storing (i) host data in at least some of thesource data objects from the context of the source VSP and (ii) copiesof the host data in at least some of the destination data objects fromthe context of the destination VSP.
 5. A method as in claim 4 whereinstoring in response to the host I/O requests includes: identifying blockchanges to the source data objects and applying the block changes to thedestination data objects.
 6. A method as in claim 5 wherein the sourceVSP resides on a first physical storage processor; wherein thedestination VSP resides on a second physical storage processor; andwherein applying the block changes to the destination data objectsincludes: conveying the block changes from the first physical storageprocessor to the second physical storage processor through a wide areanetwork (WAN).
 7. A method as in claim 5 wherein each source data objectis initially in a host read/write state; wherein each destination dataobject is initially in a host read-only state; and wherein the methodfurther comprises: in response to a failover event in which replicationof a file system contained in a particular source data object to aparticular destination data object is stopped, transitioning theparticular destination data object from the host read-only state to thehost read/write state while other replication sessions of the multiplereplication sessions continue to operate.
 8. A computer program producthaving a non-transitory computer readable medium which stores a set ofinstructions to perform replication, the set of instructions, whencarried out by computerized circuitry, causing the computerizedcircuitry to perform a method of: receiving a virtual storage processor(VSP) replication command from a user, the VSP replication commandspecifying a source VSP and a destination VSP; identifying, in responseto the VSP replication command, multiple source data objects which areconfigured to store data from the context of the source VSP; and afterthe multiple source data objects are identified, automatically creatingmultiple replication sessions to replicate the multiple source dataobjects as multiple destination data objects which are configured tostore data from the context of the destination VSP, wherein aconfiguration database holds multiple VSP records corresponding tomultiple VSPs, wherein identifying the multiple source data objectsincludes (i) locating, from the configuration database, a set of VSPrecords corresponding to the source VSP and (ii) ascertaining, from theset of VSP records, the multiple source data objects which areconfigured to store data from the context of the source VSP, wherein themultiple source data objects which are configured to store data from thecontext of the source VSP include multiple file systems, wherein the setof VSP records corresponding to the source VSP includes an identifier ofeach of the multiple file systems and a set of host interfaces throughwhich the multiple file systems are accessed, wherein ascertaining themultiple source data objects includes constructing a list of lower-deckfiles from the set of VSP records, each lower-deck file on the listbeing one of the multiple source data objects, wherein at least somelower-deck files contain upper-deck file systems of upper-deck files;and wherein the method further comprises, prior to creating the multiplereplication sessions, mounting the upper-deck file systems to a rootfile system of the source VSP.
 9. A computer program product as in claim8 wherein a VSP configuration file system is contained within aparticular lower-deck file, the VSP configuration file system having VSPconfiguration files which store VSP configuration data; and whereincreating the multiple replication sessions includes: establishing a VSPconfiguration file system replication session to replicate the VSPconfiguration file system to the destination VSP.
 10. A computer programproduct as in claim 8 wherein a set of user file systems is containedwithin a set of lower-deck files, the set of user files systems havinguser files which store host data; and wherein creating the multiplereplication sessions further includes: establishing a set of user filesystem replication sessions to replicate the set of user file systems tothe destination VSP, each user file system replication session being astandalone session which is independent of the other user file systemreplication sessions.
 11. A computer program product as in claim 8,further comprising: in response to host input/output (I/O) requests andduring the multiple replication sessions, storing (i) host data in atleast some of the source data objects from the context of the source VSPand (ii) copies of the host data in at least some of the destinationdata objects from the context of the destination VSP.
 12. A computerprogram product as in claim 11 wherein storing in response to the hostI/O requests includes: identifying block changes to the source dataobjects and applying the block changes to the destination data objects.13. An electronic apparatus, comprising: memory; and control circuitrycoupled to the memory, the memory storing instructions which, whencarried out by the control circuitry, cause the control circuitry to:receive a virtual storage processor (VSP) replication command from auser, the VSP replication command specifying a source VSP and adestination VSP, identify, in response to the VSP replication command,multiple source data objects which are configured to store data from thecontext of the source VSP, and after the multiple source data objectsare identified, automatically create multiple replication sessions toreplicate the multiple source data objects as multiple destination dataobjects which are configured to store data from the context of thedestination VSP, wherein a configuration database holds multiple VSPrecords corresponding to multiple VSPs, wherein the control circuitry,caused to identify the multiple source data objects, is further causedto (i) locate, from the configuration database, a set of VSP recordscorresponding to the source VSP and (ii) ascertain, from the set of VSPrecords, the multiple source data objects which are configured to storedata from the context of the source VSP, wherein the multiple sourcedata objects which are configured to store data from the context of thesource VSP include multiple file systems, wherein the set of VSP recordscorresponding to the source VSP includes an identifier of each of themultiple file systems and a set of host interfaces through which themultiple file systems are accessed, wherein the control circuitryconstructed and arranged to ascertain the multiple source data objectsis further constructed and arranged to construct a list of lower-deckfiles from the set of VSP records, each lower-deck file on the listbeing one of the multiple source data objects, wherein at least somelower-deck files contain upper-deck file systems of upper-deck files;and wherein, prior to creating the multiple replication sessions, thecontrol circuitry is further constructed and arranged to mount theupper-deck file systems to a root file system of the source VSP.
 14. Amethod as in claim 1, further comprising: after creating the multiplereplication sessions, attempting to maintain the replication sessions inan ongoing manner so that, as new data is added to the source dataobjects during continued operation of the source VSP, the new data isthen replicated automatically to the destination data objects.
 15. Amethod as in claim 14 wherein attempting to maintain the replicationsessions in the ongoing manner includes: sustaining a lasting set ofdata pathways from the source data objects which form a productionversion of data to the destination data objects which form a replicaversion of data.
 16. A method as in claim 15 wherein attempting tomaintain the replication sessions in the ongoing manner furtherincludes: moving data through the lasting set of data pathways over timeto concurrently maintain the new data in the source data objects and inthe destination data objects in a same format.
 17. The method of claim1, wherein the processing circuitry is provided in the form of aphysical storage processor having memory, wherein the source VSP is oneof the multiple VSPs operating in the memory of the physical storageprocessor, wherein the VSP replication command specifies the source VSPbut no other VSP operating in the memory of the physical storageprocessor, and wherein the multiple source data objects are configuredto store data from the context of the source VSP but from none of theother VSPs operating in the memory of the physical storage processor.18. The method of claim 17, where each VSP operating in the memory ofthe physical storage processor has its own namespace and network addressthat are independent of namespaces and network addresses of other VSPsoperating in the memory of the physical storage processor.